Post-Dieselgate: Evidence of NOx Emission Reductions Using On-Road Remote Sensing
On-road remote sensing confirms 30–36% NOx emission reductions from Volkswagen Group EA189 engines following post-Dieselgate hardware and software fixes.
Abstract
Post-Dieselgate: Evidence of NOx Emission Reductions Using On-Road Remote Sensing
Environmental Science & Technology Letters, Vol. 7, Issue 6, pp. 382–387, 2020
The Dieselgate scandal which broke in September 2015 demonstrated that vehicle manufacturers, such as the Volkswagen Group (VWG), engaged in software-based manipulation which led to vehicles passing laboratory-based emission testing limits but were far more polluting while being driven on roads. In this study, we use over 23,000 on-road remote sensing measurements of light-duty Euro 5 diesel vehicles in the United Kingdom between 2012 and 2018 to investigate whether there is evidence of NOx emission changes following the Dieselgate scandal. We find that VWG vehicles with the ‘Dieselgate-affected’ EA189 engine demonstrated anomalous NOx emission behaviour between the pre- and post-Dieselgate periods which was not observed in other vehicle makes or models. The anomalous changes can be explained by voluntary VWG hardware and software fixes. The 1.6 L engine vehicles, which received a combined hardware and software fix, showed a 36% reduction in NOx emissions, and the 2.0 L engine vehicles, which received a software-only fix, showed a 30% reduction when controlling for ambient temperature. These results suggest that even minor changes or upgrades can considerably reduce NOx emissions, which has implications for future emission control activities and local air quality.